1. Field of the Invention
The present invention relates to a vibration damping technique for a disk device such as an optical disk device or an magneto-optical disk device for use in audio apparatuses, video apparatuses, information apparatuses, and various precision apparatuses for on-vehicle uses and consumer uses, and in particular, the present invention relates to a viscous fluid-sealed damper for damping vibration of a supported body such as a mechanical chassis formed by a motor, an optical pickup, a disk table, etc.
2. Description of the Related Art
A disk device is a precision device which brings an optical pickup or the like close to a disk being rotated at high speed by a motor to record or reproduce information on or from the disk. Thus, the disk device is vulnerable to external vibration transmitted from the outside of the apparatus and to internal vibration generated by rotation of an eccentric disk, and it is necessary to prevent a malfunction due to such vibration. In view of this, it is common practice to provide a viscous fluid-sealed damper between a mechanical chassis on which a disk table or the like is mounted and a casing being a supporting body to thereby damp vibration of the mechanical chassis.
As shown in FIG. 29, for example, in JP 2000-220681 A or JP 2001-57068 A, such a conventional viscous fluid-sealed damper 1 is mounted between a mechanical chassis 4 and a casing 7, with a flexible portion 3 of a sealing container 2 being fixed to a hard mounting shaft 5 provided on the mechanical chassis 4, and a lid portion 6 of the sealing container 2 being fixed to the casing 7 by a mounting screw N. On the other hand, one end of each suspension spring 8, the other end of which is mounted to the casing 7, is mounted to the mechanical chassis 4 which is thereby supported in a floating state within the casing 7. In a disk device 9, both the viscous fluid-sealed dampers 1 and the suspension springs 8 are used, whereby the mechanical chassis 4 is elastically supported in a floating state within the casing 7.
As shown in FIG. 30, a viscous fluid 10 such as silicone oil is sealed in the sealing container 2 of each viscous fluid-sealed damper 1. The sealing container 2 has a cylindrical peripheral wall portion 11 formed of hard thermoplastic resin, one end of which is sealed by the flexible portion 3 formed of a thermoplastic elastomer and the other end of which equipped with a flange is sealed by the lid portion 6 formed of the same thermoplastic resin as that forming the peripheral wall portion 11. The flexible portion 3 has a bottomed cylindrical agitation tube portion 12, which is equipped with an accommodation recess 13. The peripheral wall portion 11 and the flexible portion 3 are thermally fusion-bonded to each other through two-color molding, and the peripheral wall portion 11 and the lid portion 6 are fixed to each other through ultrasonic fusion-bonding.
When vibration is applied to the disk device 9, the agitation tube portion 12, which is integral with the mounting shaft 5 inserted into the accommodation recess 13, is caused to move vertically and horizontally (three-dimensionally) to agitate the viscous fluid 10 sealed in the sealing container 2 to thereby generate viscous resistance, whereby the vibration damping effect of the viscous fluid-sealed damper 1 is exerted.
In the viscous fluid-sealed damper 1, the sealing container 2 is formed of a thermoplastic material, so the flexible portion 3, the peripheral wall portion 11, and the lid portion 6 can be molded in a short time, and the fixing of the flexible portion 3 and the peripheral wall portion 11 to each other and the fixing of the peripheral wall portion 11 and the lid portion 6 to each other can be effected through thermally fusion-bonding at the time of molding and ultrasonic fusion-bonding, respectively, as stated above, thereby advantageously providing high productivity. However, a thermoplastic elastomer has a problem in that the degree of freedom in terms of material selection is rather low. For example, to effect firm fixation between the flexible portion 3, whose fixation area is small, and the peripheral wall portion 11, the thermoplastic elastomer and the thermoplastic resin that can be used as materials are limited. Further, regarding the thermoplastic elastomer of the flexible portion 3, it is rather difficult to select a material having vibration damping performance, vibration resistance, gas permeation resistance, temperature dependence, etc.
To overcome the above problem, a method is available according to which the flexible portion 3, the peripheral wall portion 11, and the lid portion 6 forming the sealing container 2 are formed of the same thermosetting elastomer. In this method, there is no need to fusion-bond the members to each other, and it is not necessary to take into consideration the combination of members allowing fusion-bonding, so it is possible to widen the material selection range. Thus, by selecting a thermosetting elastomer depending on the requisite performance, it is advantageously possible to realize a viscous fluid-sealed damper superior in vibration damping performance, vibration resistance, gas permeation resistance, temperature dependence, etc. However, since the members are fixed to each other by adhesive, long production time and high cost are required. Further, if, when filling the sealing container 2 with the viscous fluid 10, the viscous fluid 10 is allowed to adhere to the fixation surfaces of the members, defective adhesion occurs between the peripheral wall portion 11 and the lid portion 6, which leads to leakage of the viscous fluid 10.